1. Field of the Invention
The present invention relates to an external rotor small electric motor having a rotor jacket of hardened steel as a hysteresis ring surrounding the stator.
2. Brief Description of the Background of the Invention Including Prior Art
In a conventional motor of this type an end shield is provided for the rotor shaft attachment at the front side of the rotor, and at the front side of the rotor a soft iron support is provided for the end shield in order to assure that the desired cylinder symmetrical interaction of the hysteresis ring is not affected by hysteresis effects resulting unsymmetrically from this front side region and interacting disadvantageously. Surprisingly, however, it was found that such axial dissymmetry results in little noticeable decrease in the performance of external rotor small electrical motors, if one considers as small electrical motors such motors having a power input of less than about 30 watts and having an outer diameter and an axial length of the hysteresis ring of less than about 8 cm.